The present invention is a hydrosilation process comprising contacting a silicon hydride with an unsaturated reactant in the presence of a platinum catalyst supported on porous aluminum oxide having an acidity of pH 2 to 7. The process is particularly useful for the hydrosilation of unsaturated reactants where the unsaturation is in the internal portion of the reactant's structure, for example, as in cyclopentene and cyclohexene.
It is known in the art to produce organosilicon compounds by reacting a silicon hydride containing compound with an unsaturated organic compound in the presence of a catalyst. This reaction is commonly referred to as hydrosilation or hydrosilylation. Typically the catalyst is platinum metal on a carbon support, a platinum compound generally in a solvent, or a platinum complex.
Speier et al., U.S. Pat. No. 2,823,218, teaches a method for the production of organosilicon compounds by reacting Si-H with a compound containing aliphatic carbon atoms linked by multiple bonds in the presence of chloroplatinic acid. Lamoreaux, U.S. Pat. No. 3,220,972, teaches a similar process, however the catalyst is a reaction product of chloroplatinic acid.
Wagner et al., U.S. Pat. No. 2,851,473, disclose a process for the production of organosilicon compounds comprising reacting an unsaturated organic compound with a platinum-gamma alumina catalyst.
One of the major problems known in the art with hydrosilation reactions is the de-activation of the catalyst prior to the completion of the reaction. One method for reactivation of the catalyst has been to expose the reaction mixture to oxygen. For example, Onopchenko et al., U.S. Pat. No. 4,578,497, teaches the use of an oxygenated platinum containing catalyst for use in hydrosilating alkylsilanes. Kleyer et al., EP Patent Application No. 0533170A1, discloses a method for controlling a hydrosilation reaction by controlling the solution concentration of oxygen in the reaction mixture, relative to the platinum present in the reaction mixture.
In addition to the problem of de-activation of the platinum catalyst, hydrosilation processes taught in the art are not particularly effective in hydrosilating internal unsaturated bonds in organic molecules.